From ec0b6d17a5f89da2182ec8e2f978c20bbedf6ae2 Mon Sep 17 00:00:00 2001 From: Florian Rommel Date: Thu, 25 Apr 2024 17:34:58 +0200 Subject: scripts/gdb: fix failing KGDB detection during probe Patch series "scripts/gdb: Fixes for $lx_current and $lx_per_cpu". This series fixes several bugs in the GDB scripts related to the $lx_current and $lx_per_cpu functions. The changes were tested with GDB 10, 11, 12, 13, and 14. Patch 1 fixes false-negative results when probing for KGDB Patch 2 fixes the $lx_per_cpu function, which is currently non-functional in QEMU-GDB and KGDB. Patch 3 fixes an additional bug in $lx_per_cpu that occurs with KGDB. Patch 4 fixes the incorrect detection of the current CPU number in KGDB, which silently breaks $lx_per_cpu and $lx_current. This patch (of 4): The KGDB probe function sometimes failed to detect KGDB for SMP machines as it assumed that task 2 (kthreadd) is running on CPU 0, which is not necessarily the case. Now, the detection is agnostic to kthreadd's CPU. Link: https://lkml.kernel.org/r/20240425153501.749966-1-mail@florommel.de Link: https://lkml.kernel.org/r/20240425153501.749966-2-mail@florommel.de Signed-off-by: Florian Rommel Cc: Andrew Jones Cc: Deepak Gupta Cc: Jan Kiszka Cc: Kieran Bingham Cc: Kuan-Ying Lee Cc: Palmer Dabbelt Signed-off-by: Andrew Morton --- scripts/gdb/linux/utils.py | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'scripts/gdb/linux') diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py index 7d5278d815fa..245ab297ea84 100644 --- a/scripts/gdb/linux/utils.py +++ b/scripts/gdb/linux/utils.py @@ -196,7 +196,7 @@ def get_gdbserver_type(): def probe_kgdb(): try: thread_info = gdb.execute("info thread 2", to_string=True) - return "shadowCPU0" in thread_info + return "shadowCPU" in thread_info except gdb.error: return False -- cgit v1.2.3-70-g09d2 From db08c53fdd542bb7f83bd57c3cfa3e1b95c9b54d Mon Sep 17 00:00:00 2001 From: Florian Rommel Date: Thu, 25 Apr 2024 17:34:59 +0200 Subject: scripts/gdb: fix parameter handling in $lx_per_cpu Before, the script tried to get the address by constructing a pointer to the parameter (by name). However, since GDB now passes the parameter as a GdbValue, we cannot get its name. Instead, we retrieve the address through GdbValue's address attribute. Before: >>> p $lx_per_cpu(cpu_info) Traceback (most recent call last): File "./scripts/gdb/linux/cpus.py", line 152, in invoke var_ptr = gdb.parse_and_eval("&" + var_name.string()) ^^^^^^^^^^^^^^^^^ gdb.error: Trying to read string with inappropriate type `struct cpuinfo_x86'. Link: https://lkml.kernel.org/r/20240425153501.749966-3-mail@florommel.de Signed-off-by: Florian Rommel Cc: Andrew Jones Cc: Deepak Gupta Cc: Jan Kiszka Cc: Kieran Bingham Cc: Kuan-Ying Lee Cc: Palmer Dabbelt Signed-off-by: Andrew Morton --- scripts/gdb/linux/cpus.py | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'scripts/gdb/linux') diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py index cba589e5b57d..2b51a3abd363 100644 --- a/scripts/gdb/linux/cpus.py +++ b/scripts/gdb/linux/cpus.py @@ -152,9 +152,8 @@ Note that VAR has to be quoted as string.""" def __init__(self): super(PerCpu, self).__init__("lx_per_cpu") - def invoke(self, var_name, cpu=-1): - var_ptr = gdb.parse_and_eval("&" + var_name.string()) - return per_cpu(var_ptr, cpu) + def invoke(self, var, cpu=-1): + return per_cpu(var.address, cpu) PerCpu() -- cgit v1.2.3-70-g09d2 From 7566b063e9e4af908123ebe8b80cc0d0c7429507 Mon Sep 17 00:00:00 2001 From: Florian Rommel Date: Thu, 25 Apr 2024 17:35:00 +0200 Subject: scripts/gdb: make get_thread_info accept pointers get_thread_info ($lx_thread_info) only accepted a dereferenced task parameter. Passing a pointer to a task_struct (like $lx_per_cpu does with KGDB) threw an exception. With this patch, both (dereferenced values and pointers) are accepted. Before (on x86, KGDB): >>> p $lx_per_cpu(cpu_info) Traceback (most recent call last): File "./scripts/gdb/linux/cpus.py", line 158, in invoke return per_cpu(var_ptr, cpu) ^^^^^^^^^^^^^^^^^^^^^ File "./scripts/gdb/linux/cpus.py", line 42, in per_cpu cpu = get_current_cpu() ^^^^^^^^^^^^^^^^^ File "./scripts/gdb/linux/cpus.py", line 33, in get_current_cpu return tasks.get_thread_info(tasks.get_task_by_pid(tid))['cpu'] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "./scripts/gdb/linux/tasks.py", line 88, in get_thread_info if task.type.fields()[0].type == thread_info_type.get_type(): ~~~~~~~~~~~~~~~~~~^^^ IndexError: list index out of range Link: https://lkml.kernel.org/r/20240425153501.749966-4-mail@florommel.de Signed-off-by: Florian Rommel Cc: Andrew Jones Cc: Deepak Gupta Cc: Jan Kiszka Cc: Kieran Bingham Cc: Kuan-Ying Lee Cc: Palmer Dabbelt Signed-off-by: Andrew Morton --- scripts/gdb/linux/tasks.py | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'scripts/gdb/linux') diff --git a/scripts/gdb/linux/tasks.py b/scripts/gdb/linux/tasks.py index 6793d6e86e77..62348397c1f5 100644 --- a/scripts/gdb/linux/tasks.py +++ b/scripts/gdb/linux/tasks.py @@ -85,7 +85,7 @@ thread_info_type = utils.CachedType("struct thread_info") def get_thread_info(task): thread_info_ptr_type = thread_info_type.get_type().pointer() - if task.type.fields()[0].type == thread_info_type.get_type(): + if task_type.get_type().fields()[0].type == thread_info_type.get_type(): return task['thread_info'] thread_info = task['stack'].cast(thread_info_ptr_type) return thread_info.dereference() -- cgit v1.2.3-70-g09d2 From 40eea5abbb9ccae6df55dfd94c3c85c023e2521b Mon Sep 17 00:00:00 2001 From: Florian Rommel Date: Thu, 25 Apr 2024 17:35:01 +0200 Subject: scripts/gdb: fix detection of current CPU in KGDB Directly read the current CPU number from the kgdb_active variable. Before, the active CPU was obtained through the current task, which required searching the task list for the pid of GDB's selected thread. Obtaining the pid was buggy: GDB may use selected_thread().ptid[1] (LWPID) instead of .ptid[2] (TID) to store the threads pid; see https://sourceware.org/gdb/current/onlinedocs/gdb.html/Threads-In-Python.html As a result, the detection could return the wrong CPU number, leading to incorrect results for $lx_per_cpu and $lx_current. As a side effect, the patch significantly speeds up $lx_per_cpu and $lx_current in KGDB by avoiding the task-list iteration. Link: https://lkml.kernel.org/r/20240425153501.749966-5-mail@florommel.de Signed-off-by: Florian Rommel Cc: Andrew Jones Cc: Deepak Gupta Cc: Jan Kiszka Cc: Kieran Bingham Cc: Kuan-Ying Lee Cc: Palmer Dabbelt Signed-off-by: Andrew Morton --- scripts/gdb/linux/cpus.py | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) (limited to 'scripts/gdb/linux') diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py index 2b51a3abd363..2f11c4f9c345 100644 --- a/scripts/gdb/linux/cpus.py +++ b/scripts/gdb/linux/cpus.py @@ -26,11 +26,7 @@ def get_current_cpu(): if utils.get_gdbserver_type() == utils.GDBSERVER_QEMU: return gdb.selected_thread().num - 1 elif utils.get_gdbserver_type() == utils.GDBSERVER_KGDB: - tid = gdb.selected_thread().ptid[2] - if tid > (0x100000000 - MAX_CPUS - 2): - return 0x100000000 - tid - 2 - else: - return tasks.get_thread_info(tasks.get_task_by_pid(tid))['cpu'] + return gdb.parse_and_eval("kgdb_active.counter") else: raise gdb.GdbError("Sorry, obtaining the current CPU is not yet " "supported with this gdb server.") -- cgit v1.2.3-70-g09d2